Characterization of tumor cells and their differentiation from nonmalignant host cells present at the tumor site or infiltrating the tumor that may grow as colonies in an in vitro system is necessary to efficiently analyze the effects of therapy using clonogenic cell assays. One goal of this investigation is the characterization of nonmalignant cells and colonies from human brain tumors, in order to eliminate them from the evaluation of in vitro tumor cell survival studies and permit a more accurate representation of in situ tumor response. A panel of cell identification parameters consisting of histochemical stains, antigenic studies, functional criteria and morphological characteristics will be used to identify normal host cells. Glial cells will be identified by the presence of glial fibrillary acidic protein and recognition by hybridoma-secreted, glioma-associated monoclonal antibodies. The cells disaggregated from tumor biopsies and cells growing in early passage monolayer culture will be analyzed. The second goal of this research is the isolation and characterization of tumor cells from various regions of human brain tumors to gain increased knowledge of tumor heterogeneity and the influence of specimen selection on the clonogenic cell assay. Clonogenic cells will be considered tumor "stem" cells if self-renewal is demonstrated on serial subculture. Cell cultures have been initiated from two or three histologically distinct regions from a variety of tumors and are being analyzed for cell morphology, the cell characterization parameters outlined above and for drug sensitivity.